When a webhook is triggered, a call is made in a HTTPPOST with a
Content-Type:application/x-www-form-urlencoded, and the JSON encoded payload
is given as argument in the payload parameter of the request.
The endpoint can use the information included in this payload in order to perform
various tasks (continuous deployment, backup…).

You can see the status of the response (200OK, 404NotFound…) in the logs
section of each webhook.